Photolithographic stepper and/or scanner machines including cleaning devices and methods of cleaning photolithographic stepper and/or scanner machines

ABSTRACT

Stepper and/or scanner machines including cleaning devices and methods for cleaning stepper and/or scanner machines are disclosed herein. In one embodiment, a stepper and/or scanner machine includes a housing, an illuminator, a lens, a workpiece support, a cleaning device for removing contaminants from the workpiece support, and a stage carrying the workpiece support. The stage and/or cleaning device is movable to selectively position the workpiece support proximate to the cleaning device. It is emphasized that this Abstract is provided to comply with the rules requiring an abstract. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.

TECHNICAL FIELD

The present invention is related to stepper and/or scanner machinespatterning features on microfeature workpieces. More particularly, theinvention is directed to stepper and/or scanner machines includingcleaning devices and methods of cleaning stepper and/or scannermachines.

BACKGROUND

Photolithography is one of the primary processes used in the manufactureof microelectronic devices (e.g., dies) on semiconductor wafers ormicromechanical devices. In photolithography, a stepper or scannermachine exposes photosensitive materials to pattern the design of thefeatures onto the semiconductor wafer's surface. A conventional stepperor scanner machine includes a wafer chuck, an illuminator to projectlight or other radiation, a lens to focus the light, and a reticle. Thereticle can be a glass plate with a layer of chrome having a patterncorresponding to the layout of features that are to be constructed onthe wafer. In a typical photolithography process, a wafer having a layerof photoresist material is positioned under the lens in the stepper orscanner machine. Next, the illuminator projects a pattern of light ontoa portion of the wafer through the corresponding pattern on the reticleand the lens. The light changes the material characteristic of theexposed areas of the photoresist layer to make the exposed areas more orless susceptible to a developing solution. The stepper or scannermachine then positions another portion of the wafer under the reticleand repeats the exposure operation until the entire wafer has beenpatterned.

In a subsequent operation, the photoresist layer is typically baked andthen developed to create the desired pattern in the resist layer forforming the features. Accordingly, the pattern must be formed in theproper location on the photoresist layer and with very precisedimensions to form very small features of 0.11 μm or less. Errors inphotolithography can cause many problems including distorted patterns,misplaced patterns, and other defects. These types of errors canultimately result in defective microelectronic devices. Moreover, as thefeature sizes decrease, slight imperfections or misalignments can resultin defects.

A common cause of errors in photolithography is contamination of thewafer chuck in the stepper or scanner machine. More specifically,particles or other contaminants from other processes, such aschemical-mechanical planarization, vapor depositions, etc., may remainon the wafer as it is loaded into the stepper or scanner machine. Thesecontaminants can be left on the support surface of the wafer chuck,which prevents subsequent wafers from being properly positioned in thewafer chuck. For example, FIG. 1 is a schematic side cross-sectionalview of a wafer 20, a wafer chuck 50, and a particle P between the wafer20 and the wafer chuck 50 (shown exaggerated for illustrative purposes).The wafer chuck 50 includes a plurality of holes 54 coupled to a vacuumpump 58 to hold the wafer 20 against the chuck 50. The particle P causesthe wafer 20 to deform as the vacuum pump 58 draws the water 20 againstthe chuck 50. This portion of the wafer 20, for example, can projectoutward from the wafer chuck 50 a distance T. As the feature sizesdecrease, even a very small deformation of the wafer 20 may be greaterthan the field depth of the lens such that the lens may not properlyfocus the pattern of light on the area of the wafer 20 over the particleP. Improper focusing on a region of the wafer causes what is known as afocus spot. If focus spots are detected at a consistent location onseveral wafers, the wafer chuck is likely contaminated and must becleaned.

One problem with existing stepper and scanner machines is that accessingthe wafer chuck for cleaning is difficult and the stepper and scannermachines must be recalibrated after each cleaning. More specifically,the cleaning process includes shutting down the stepper or scannermachine, removing one or more panels of the housing, sliding the waferchuck out of the housing, and cleaning the chuck manually. After thewafer chuck is manually cleaned, the chuck is repositioned in thestepper or scanner machine and the panels are reattached. However,before the stepper or scanner machine can continue processing wafers, itmust be recalibrated. Recalibrating stepper and scanner machines is adifficult and time-consuming process that may also require processingtarget wafers to ensure the stepper or scanner machine is properlyregistered. The entire process requires significant downtime andconsequently causes a significant reduction in throughput. Accordingly,there exists a need to reduce the downtime required to clean the stepperand/or scanner machine.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side cross-sectional view of a wafer in acontaminated wafer chuck.

FIG. 2 is a schematic side view of a stepper or scanner machineincluding a cleaning device in accordance with one embodiment of theinvention.

FIG. 3 is a schematic side cross-sectional view of a portion of thestepper or scanner machine and the cleaning device of FIG. 2.

FIG. 4 is a schematic side cross-sectional view of a portion of astepper or scanner machine including a cleaning device in accordancewith another embodiment of the invention.

FIG. 5 is a schematic side view of a stepper or scanner machineincluding a cleaning device in accordance with another embodiment of theinvention.

DETAILED DESCRIPTION

A. Overview

The present invention is directed toward stepper and/or scanner machinesfor processing microfeature workpieces and methods of cleaning stepperand/or scanner machines. The term “microfeature workpiece” is usedthroughout to include substrates in or on which microelectronic devices,micromechanical devices, data storage elements, and other features arefabricated. For example, microfeature workpieces can be semiconductorwafers, glass substrates, insulated substrates, or many other types ofsubstrates. Several specific details of the invention are set forth inthe following description and in FIGS. 2-5 to provide a thoroughunderstanding of certain embodiments of the invention. One skilled inthe art, however, will understand that the present invention may haveadditional embodiments, or that other embodiments of the invention maybe practiced without several of the specific features explained in thefollowing description.

One aspect of the invention is directed to stepper or scanner machinesfor processing microfeature workpieces. In one embodiment, a stepper orscanner machine includes a housing, an illuminator, a lens, a workpiecesupport, a cleaning device for removing contaminants from the workpiecesupport, and a stage carrying the workpiece support. The stage and/orcleaning device is movable to selectively position the workpiece supportproximate to the cleaning device. In one aspect of this embodiment, thestepper or scanner machine further includes a positioning device coupledto the cleaning device to move the cleaning device relative to thehousing. Alternatively, the cleaning device may be fixed relative to thehousing. In another aspect of this embodiment, the stepper or scannermachine further includes a vacuum pump operably coupled to the cleaningdevice to draw contaminants from the workpiece support. The stepper orscanner machine can also include a cleaning fluid supply operablycoupled to the cleaning device to provide a cleaning fluid to theworkpiece support.

In another embodiment, a stepper or scanner machine includes aphotolithographic exposure system, a workpiece support, an internalcleaning device, and a stage carrying the workpiece support. Theworkpiece support has a recess to receive a microfeature workpiece, andthe internal cleaning device has a distal portion with a passageway forremoving contaminants from the recess of the workpiece support. Thestage and/or cleaning device is movable to position the distal portionof the cleaning device at least proximate to the recess of the workpiecesupport. In one aspect of this embodiment, the distal portion of thecleaning device includes an end effector configured to engage theworkpiece support to remove contaminants.

Another aspect of the invention is directed to methods of cleaningstepper and/or scanner machines. In one embodiment, a method includespositioning a cleaning device at least proximate to a workpiece supportwithout removing a portion of a housing of the stepper or scannermachine. The workpiece support and the cleaning device are disposedwithin the stepper or scanner machine. The method further includesremoving contaminants from the workpiece support with the cleaningdevice. In one aspect of this embodiment, removing contaminants from theworkpiece support can include engaging the workpiece support with an endeffector. In another aspect of this embodiment, removing contaminantsfrom the workpiece support includes drawing contaminants from theworkpiece support through a passageway in the cleaning device with avacuum pump. In another aspect of this embodiment, the method furtherincludes providing a cleaning fluid to the workpiece support through afirst passageway in the cleaning device and exhausting the cleaningfluid from the workpiece support through a second passageway in thecleaning device.

B. Embodiments of Stepper and/or Scanner Machines

FIG. 2 is a schematic side view of a stepper or scanner machine 100 forpatterning a photoresist layer on a microfeature workpiece W using aphotolithography process in accordance with one embodiment of theinvention. The patterns are used in the construction of microelectronicdevices, micromechanical devices, and/or other features on themicrofeature workpiece W. In the illustrated embodiment, the stepper orscanner machine 100 includes a housing 110 enclosing a workpiece support150, a lens 180, a reticle 190, and an illuminator 194. The housing 110can include a plurality of panels 112 (two of which are identifiedindividually as 112 a-b) that define an internal chamber 114. The panels112 can be removed to access the internal components of the stepper orscanner machine 100. The temperature, humidity, and other environmentalfactors in the internal chamber 114 can be precisely controlled toconsistently process microfeature workpieces under optimal conditions.

The workpiece support 150 carries the microfeature workpiece W duringthe patterning process. The workpiece support 150 can include a recess152 defined in part by a support surface 153 to receive the microfeatureworkpiece W. In one embodiment, the workpiece support 150 furtherincludes a plurality of holes 154 in the support surface 153 and avacuum line 156 connected to the holes 154. A vacuum pump 158 (shownschematically) can be coupled to the vacuum line 156 to secure themicrofeature workpiece W to the workpiece support 150 during patterning.In other embodiments, the workpiece support 150 may not include arecess, and/or the microfeature workpiece W may be secured to theworkpiece support 150 by a device other than a vacuum pump.

The reticle 190 carries the patterns to be used in constructing themicroelectronic devices, micromechanical devices, and/or other featureson the microfeature workpiece W. For example, the reticle 190 caninclude a glass plate and a layer of chrome patterned on the plate. Thelens 180 focuses the light pattern onto the workpiece W. In operation,the illuminator 194 projects light through the reticle 190 and the lens180 to change the characteristics of areas of the photoresist layerexposed to the light. The exposed areas become more or less susceptibleto removal in a developing solution. The illuminator 194 can projectultraviolet light or other types of electromagnetic radiation. Becausethe light must strike precise locations of the photoresist layer on themicrofeature workpiece W, the stepper or scanner machine 100 can alsoinclude a vibration isolation system 120 to reduce alignment andfocusing errors from vibration of the components within the housing 110.

The stepper or scanner machine 100 further includes a stage 140 to carrythe workpiece support 150, a positioning device 146 operably coupled tothe stage 140, and a controller 147 (shown schematically) to operate thepositioning device 146. The controller 147 can include acomputer-readable medium that operates the positioning device 146 tomove the stage 140 and properly align the microfeature workpiece Wrelative to the lens 180. The microfeature workpiece W is properlyaligned before exposure to the light so that the pattern is formed atthe desired location on the workpiece W. The positioning device 146 canmove the stage 140 along three orthogonal axes such as side to side (Xdirection), forward and backward (Y direction), and/or upward anddownward (Z direction). The positioning device 146 may also rotate thestage 140 about each of the axes. The stepper or scanner machine 100 canalso include a transfer mechanism 130 (shown schematically in brokenlines) to load the microfeature workpiece W onto the workpiece support150.

The stepper or scanner machine 100 further includes a cleaning device160 disposed within the housing 110 and a vacuum pump 178 (shownschematically) operably coupled to the cleaning device 160. In oneaspect of the illustrated embodiment, the cleaning device 160 removescontaminants from the workpiece support 150 so that the microfeatureworkpiece W can be properly positioned on the support 150. As describedabove, the incoming workpieces can deposit residual contaminants, suchas small particles, on the workpiece support 150. The cleaning device160 of the illustrated embodiment automatically removes contaminantsfrom the workpiece support 150 without manual ingress into the chamber114. The cleaning device 160 can accordingly prevent focus spots on themicrofeature workpiece W as described below with reference to FIG. 3without the downtime normally associated with manually cleaning theworkpiece support 150.

In one aspect of the embodiment, the cleaning device 160 is attached ata fixed position within the housing 110. Accordingly, the controller 147moves the stage 140 to position a portion of the cleaning device 160 inthe recess 152 to remove contaminants from the workpiece support 150. Inother embodiments, such as the embodiment described below with referenceto FIG. 5, the cleaning device can be movable within the housing 110 andaccordingly move toward the workpiece support 150. In the illustratedembodiment, the cleaning device 160 is shown positioned proximate to thelens 180; however, the cleaning device 160 can be positioned proximateto other components within the housing 110.

C. Embodiments of Cleaning Devices

FIG. 3 is a schematic side cross-sectional view of a portion of thestepper or scanner machine 100 and the cleaning device 160 of FIG. 2. Inthe illustrated embodiment, the cleaning device 160 includes a body 164having a passageway 166 coupled to the vacuum pump 178 and a distalportion 162 with a lower surface 170. After the microfeature workpiece W(FIG. 2) is removed from the workpiece support 150, the stage 140 canmove the workpiece support 150 so that the distal portion 162 of thecleaning device 160 is received at least partially in the recess 152.The surface 153 of the workpiece support 150 can be spaced apart fromthe lower surface 170 of the distal portion 162 to avoid damaging thecleaning device 160 or the workpiece support 150 during cleaning. Oncethe distal portion 162 is received in the recess 152, the stage 140 canmove the workpiece support 150 so that the cleaning device 160 sweepsback and forth across the recess 152 to remove the contaminants. As thedistal portion 162 moves over the contaminants, the vacuum pump 178draws the contaminants from the recess 152 through the passageway 166 ina direction D₁. This cleaning process can occur at periodic intervals,or whenever focus spots are detected on the workpieces.

In one aspect of this embodiment, the cleaning device 160 includes anend effector 172 (shown in broken lines) attached to the distal portion162. The end effector 172 engages the surface 153 of the workpiecesupport 150 to dislodge contaminants. The end effector 172 can include abrush with bristles, a pad, and/or another device depending on the typeof contaminants and the material of the workpiece support 150. Forexample, in one embodiment, the end effector 172 can include Teflon®brushes. The end effector 172 can include a plurality of apertures oropenings to allow the vacuum pump 178 to draw contaminants through theend effector 172 and into the passageway 166. In one embodiment, thestage 140 and workpiece support 150 can reciprocate back and forth sothat the end effector 172 can scrub and dislodge trapped or attachedcontaminants. In other embodiments, the cleaning device 160 may notinclude an end effector.

One feature of the stepper or scanner machine in the embodimentillustrated in FIGS. 2 and 3 is that the cleaning device is disposedwithin the housing. An advantage of this feature is that the side panelsof the housing do not need to be removed to access and clean theworkpiece support. This is an improvement over prior art stepper andscanner machines that do not have an internal cleaning device. The priorart stepper and scanner machines require significant downtime to removethe workpiece support, manually clean the workpiece support, andrecalibrate the stepper or scanner machine. In the illustratedembodiment, the housing panels and workpiece support do not need to beremoved, and the cleaning device 160 can be quickly positioned to cleanthe workpiece holder 150 by merely moving the stage 140 within itsnormal operating range. This not only reduces the time and effort toclean the workpiece support compared to manual cleaning processes, butit also reduces or eliminates the need to recalibrate the stepper orscanner machine. Consequently, the downtime required to clean thestepper or scanner machine is reduced and the throughput of the stepperor scanner machine is increased compared to conventional manual cleaningprocesses.

FIG. 4 is a schematic side cross-sectional view of a portion of astepper or scanner machine 200 including a cleaning device 260 inaccordance with another embodiment of the invention. The stepper orscanner machine 200 is generally similar to the stepper or scannermachine 100 described above with reference to FIGS. 2 and 3. Forexample, the stepper or scanner machine 200 includes a stage 140, aworkpiece support 150, and a cleaning device 260. The cleaning device260 includes a body 264 having a first passageway 266 a, a secondpassageway 266 b, and a distal portion 262. In the illustratedembodiment, the first and second passageways 266 a-b are configured in aconcentric arrangement with the first passageway 266 a surrounding thesecond passageway 266 b; however, in other embodiments, the passagewayscan have other configurations.

The stepper or scanner machine 200 can further include a cleaning fluidsupply 279 coupled to the first passageway 266 a to provide a cleaningfluid to the surface 153 of the recess 152 for removing contaminants.The cleaning fluid can include deionized water, acetone, etchants, orany other suitable fluid to remove contaminants from the recess 152. Thestepper or scanner machine 200 can further include a vacuum pump 178coupled to the second passageway 266 b to remove the cleaning fluid andthe contaminants from the surface 153 of the recess 152. The cleaningfluid accordingly flows in a direction D₂ through the first passageway266 a to the recess 152 and is exhausted in a direction D3 through thesecond passageway 266 b. The cleaning device 260 can also include an endeffector 272 (shown in broken lines) similar to the end effector 172described above with reference to FIG. 3. In other embodiments, thecleaning device can have other configurations.

D. Additional Embodiments of Stepper and/or Scanner Machines

FIG. 5 is a schematic side view of a stepper or scanner machine 300 forprocessing microfeature workpieces in accordance with another embodimentof the invention. The stepper or scanner machine 300 can be generallysimilar to the stepper or scanner machine 100 described above withreference to FIGS. 2 and 3. For example, the stepper or scanner machine300 includes a housing 110 enclosing a stage 140, a workpiece support150, a lens 180, a reticle 190, and an illuminator 194. The stepper orscanner machine 300 further includes a controller 147, a cleaning device160 and a positioning device 361 operably coupled to the controller 147and the cleaning device 160. The controller 147 can operate thepositioning device 361 to move the cleaning device 160 along the X, Y,and/or Z axes to position the distal portion 162 of the cleaning device160 in the recess 152 of the workpiece support 150. Moreover, thecontroller 147 can operate the positioning device 361 to sweep thecleaning device 160 back and forth across the recess 152 to removecontaminants from the workpiece support 150 in a cleaning cycle.Accordingly, after the transfer mechanism 130 removes the microfeatureworkpiece from the workpiece support 150, the stage 140 moves theworkpiece support 150 along the X axis toward the cleaning device 160.Once the stage 140 has moved the workpiece support 150 proximate to thecleaning device 160, the positioning device 361 moves the cleaningdevice 160 to remove contaminants from the recess 152. In otherembodiments, the positioning device may not move the cleaning devicealong the X, Y, and Z axes. For example, the positioning device may onlymove the cleaning device along the Z axis.

From the foregoing, it will be appreciated that specific embodiments ofthe invention have been described herein for purposes of illustration,but that various modifications may be made without deviating from thespirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1-43. (canceled)
 44. A method of patterning microfeature workpieces witha stepper or scanner machine, the method comprising: patterning a firstmicrofeature workpiece by exposing the first workpiece to a source ofradiation; positioning a cleaning device at least proximate to aworkpiece support without removing a portion of a housing of themachine, the workpiece support and the cleaning device being disposedwithin the housing; removing contaminants from the workpiece supportwith the cleaning device; and patterning a second microfeature workpieceby exposing the second workpiece to the source of radiation.
 45. Themethod of claim 44 wherein removing contaminants from the workpiecesupport comprises drawing contaminants from the workpiece supportthrough a passageway in the cleaning device with a vacuum pump.
 46. Themethod of claim 44 wherein the cleaning device comprises an endeffector, and wherein removing contaminants from the workpiece supportcomprises engaging the workpiece support with the end effector.
 47. Amethod of patterning microfeature workpieces with a stepper or scannermachine, the stepper or scanner machine including a housing, a cleaningdevice within the housing, a radiation source within the housing, and aworkpiece support within the housing, the method comprising: patterninga first microfeature workpiece by exposing the first workpiece to theradiation source; moving at least one of the cleaning device or theworkpiece support so that a distal portion of the cleaning device ispositioned at least proximate to a recess in the workpiece support;removing contaminants from the recess in the workpiece support via apassageway in the cleaning device; and patterning a second microfeatureworkpiece by exposing the second workpiece to the radiation source. 48.The method of claim 47 wherein the cleaning device comprises an endeffector, and wherein removing contaminants from the recess comprisesengaging the workpiece support with the end effector.
 49. The method ofclaim 47 wherein removing contaminants from the recess comprises drawingcontaminants from the recess through the passageway in the cleaningdevice with a vacuum pump.
 50. A method of patterning microfeatureworkpieces with a stepper or scanner machine, the method comprising:patterning a first microfeature workpiece by exposing the firstworkpiece to a source of radiation; within a housing of the stepper orscanner machine, automatically positioning a workpiece support proximateto a cleaning device; removing contaminants from the workpiece supportwith the cleaning device; and patterning a second microfeature workpieceby exposing the second workpiece to the source of radiation.
 51. Themethod of claim 50 wherein the cleaning device comprises an endeffector, and wherein removing contaminants from the workpiece supportcomprises engaging the workpiece support with the end effector.
 52. Themethod of claim 50 wherein removing contaminants from the workpiecesupport comprises drawing contaminants from the workpiece supportthrough a passageway in the cleaning device with a vacuum pump.
 53. Amethod of monitoring a stepper or scanner machine, the stepper orscanner machine including a housing, a cleaning device within thehousing, and a workpiece support within the housing, the methodcomprising: patterning a microfeature workpiece; determining if themicrofeature workpiece contains a focus spot after patterning themicrofeature workpiece; if the microfeature workpiece contains the focusspot, moving at least one of the cleaning device and the workpiecesupport so that a distal portion of the cleaning device is positioned atleast proximate to a region of the workpiece support corresponding tothe location of the focus spot on the microfeature workpiece; and if themicrofeature workpiece contains the focus spot, removing contaminantsfrom the workpiece support via a passageway in the cleaning device. 54.The method of claim 53 wherein removing contaminants from the workpiecesupport comprises drawing contaminants from the workpiece supportthrough the passageway in the cleaning device with a vacuum pump. 55.The method of claim 53 wherein the cleaning device comprises an endeffector, and wherein removing contaminants from the workpiece supportcomprises engaging the workpiece support with the end effector.
 56. Themethod of claim 44 wherein removing contaminants from the workpiecesupport comprises providing a cleaning fluid to the workpiece supportand exhausting the cleaning fluid from the workpiece support.
 57. Themethod of claim 44 wherein positioning the cleaning device at leastproximate to the workpiece support comprises moving the cleaning devicerelative to the housing.
 58. The method of claim 44 wherein positioningthe cleaning device at least proximate to the workpiece supportcomprises moving the workpiece support relative to the housing withoutmoving the cleaning device relative to the housing.
 59. The method ofclaim 47 wherein moving at least one of the cleaning device or theworkpiece support comprises moving at least one of the cleaning deviceor the workpiece support without removing a portion of the housing. 60.The method of claim 47 wherein removing contaminants from the recess inthe workpiece support comprises providing a cleaning fluid to theworkpiece support and exhausting the cleaning fluid from the workpiecesupport.
 61. The method of claim 50 wherein automatically positioningthe workpiece support proximate to the cleaning device comprising movingthe cleaning device relative to the housing.
 62. The method of claim 50wherein removing contaminants from the workpiece support comprisesproviding a cleaning fluid to the workpiece support and exhausting thecleaning fluid from the workpiece support.
 63. The method of claim 53wherein removing contaminants from the workpiece support comprisesproviding a cleaning fluid to the workpiece support and exhausting thecleaning fluid from the workpiece support.